MicrobeHunter.com Microscopy Forum

The Biolam M that I recently purchased, and am hoping to restore, was made in the USSR

As readers [especially MicroBob] will be aware, I have had some difficulty with the illumination; and the images produced so far have been disappointing.

My previous posts on the matter have been rather confused; so let's first put the record straight :

There are four epi-objectives, all of which have dark-field capability by virtue of a ring ‘condenser’
... unfortunately, I do not have the < TN > insert for the microscope head, so I cannot currently use that facility.
Rather strangely; in two of the objectives this condenser is catadioptric, in the other two it is catoptric only.

The < CN > insert [which I do have] provides true axial illumination, using the objective as its own bright-field condenser.

The main illuminator has a Tungsten Halogen bulb, followed by a large lens [adjustable for position to suit either mode of operation] and an iris diaphragm ... There is then a holder for optional filters, and a small lens mounted in a ‘spider’.
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This is all fairly standard stuff : But it doesn’t work

Today, I noticed the fundamental design error [or perhaps the Soviet Plot]
... It is impossible to centre the lamp !!

Here are two flatbed scans to illustrate the problem:
The lamp filament is approximately centred in the lamphouse ... But that places it high above the optical axis of the illuminator.
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My first thought was that it must be the wrong bulb ... BUT the filament is correctly positioned with respect to the aperture in the mask, so the wretched thing must be designed wrong.

I can fix this quite easily, by fitting either an LED, or a fibre optic source ... but I’m still struggling to understand how it got through design and production with such a fundamental flaw.

Comments would be welcome.

MichaelG.

The bulb is pretty much centered in its housing (just measured it on my screen) - if no movement is possible then perhaps the outer housing is from another lamphouse?

75RR wrote: ↑

Mon Apr 13, 2020 7:50 pm

Can you turn it 180 degrees?

Yes ... or 90, or 270 ... All alternative positions are worse.

Thanks for the thought though.

MichaelG.
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Edit: it seems I have answered a question which is no longer there !

Can you turn it 180 degrees?

Visually it looked higher that it is, amended my post when I realized but you had caught my original post before then. Sorry

Michael, the large bore hole in the metal plate shown in the bottom photo seems to function as a "bayonet" connector. Could it be that the lamp fixture was actually meant to pass through it, I mean that the lamp house is incorrectly assembled ? I appologise if this is a silly question, have never seen Soviet microscopes .

75RR wrote: ↑

Mon Apr 13, 2020 7:50 pm

The bulb is pretty much centered in its housing (just measured it on my screen) - if no movement is possible then perhaps the outer housing is from another lamphouse?

That’s why I did flatbed scans in preference to more illustrative photos.

Anything is possible, I suppose ... but so far as I can tell, it’s original.

MichaelG.

Hobbyst46 wrote: ↑

Mon Apr 13, 2020 8:01 pm

Michael, the large bore hole in the metal plate shown in the bottom photo seems to function as a "bayonet" connector. Could it be that the lamp fixture was actually meant to pass through it, I mean that the lamp house is incorrectly assembled ? I appologise if this is a silly question, have never seen Soviet microscopes .

Yes, the lamp fixture bayonets into that hole
The lamp can be centred within its mount ... but only by a couple of millimetres.

The large hole in the box [your plate] is correctly positioned for the optical axis ... it’s just that the lamp filament is way above where it needs to be.

I will take some illustrative photos tomorrow.

MichaelG.

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Edit: Meanwhile ... as mentioned on the ‘silicon chip’ thread

P.S. __ It’s similar to the one being restored here:

http://www.mikroskopfreunde-nordhessen. ... en/Noa.pdf

... but with a different set of faults.

75RR wrote: ↑

Mon Apr 13, 2020 8:00 pm

Can you turn it 180 degrees?

Visually it looked higher that it is, amended my post when I realized but you had caught my original post before then. Sorry

No problem ... all observations [even fleeting ones] are most welcome.

MichaelG.

wrong bulb or socket? scientific bulbs often include a filament to some reference point measurement. there are instances of two basically identical bulbs with the filament either higher or lower in the envelope.

apochronaut wrote: ↑

Mon Apr 13, 2020 10:30 pm

wrong bulb or socket? scientific bulbs often include a filament to some reference point measurement. there are instances of two basically identical bulbs with the filament either higher or lower in the envelope.

That was my initial thought; but [as I mentioned] the filament aligns nicely with the aperture in the mask.

Sorry; it’s not obvious from the scan, but the tall masking plate is attached to the lamp-holder, and moves with the bulb ... whilst the other shielding is attached to the housing:
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Difficult as it is to believe: It looks like the masking plate was made to match the chosen bulb without appreciating that the filament position was wrong.

Detail photos to follow ... probably this evening [U.K. time]

MichaelG.

This overlay of the scans should help illustrate the extent of the problem:
. .

MichaelG.

As promised ... A few illustrative views of the lamphouse:
. . . . . .

There are more available, if anything is still not clear ... but I think these will probably suffice.

MichaelG.

... and one of the lampholder:
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Again: There are more available, if anything is still not clear ... but I think this one will probably suffice.

... Quite simply: the filament needs to be at the centre-height of that bayonet fitting !!

MichaelG.

Don't suppose you can fit it upside down?

Michael, this is a strange beast.
These isolation tubes look like PTFE to me. PTFE tubes on a Soviet Russian fixture ? Is this original or an improvised hybrid ? and the asbestos layer ?

BTW, one of several articles about the LOMO, by Ian Walker in Micscape, mentions the weak points of the Russian bulb, at least in comparison to a more modern bulb. Although he did not mention the "way off optical axis" problem.

Difficult as it is to believe: It looks like the masking plate was made to match the chosen bulb without appreciating that the filament position was wrong.

I have no difficulties to believe. I have owned several Lomo microscopes of different types: The optics is quite fine but poor machining of the mechanical parts and assembly is very common. I would say this is just normal.

Leitzcycler wrote: ↑

Tue Apr 14, 2020 6:27 pm

Difficult as it is to believe: It looks like the masking plate was made to match the chosen bulb without appreciating that the filament position was wrong.

I have no difficulties to believe. I have owned several Lomo microscopes of different types: The optics is quite fine but poor machining of the mechanical parts and assembly is very common. I would say this is just normal.

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I think that probably sums-it-up nicely

MichaelG.

Hobbyst46 wrote: ↑

Tue Apr 14, 2020 6:17 pm

Michael, this is a strange beast.
These isolation tubes look like PTFE to me. PTFE tubes on a Soviet Russian fixture ? Is this original or an improvised hybrid ? and the asbestos layer ?

Thanks for the thoughts, but I can see nothing to suggest that any of this is non-original.

MichaelG.

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Here’s another image for the ‘Black Museum’ ... it’s all pristine, but made wrong !!
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75RR wrote: ↑

Tue Apr 14, 2020 6:11 pm

Don't suppose you can fit it upside down?

The bayonet will fit in any of the four orientations but none of them puts the filament on axis
... and the mask plate is obviously only designed for ‘right way up’

MichaelG.
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Note: I use the word ‘designed’ very loosely, here

Michael,
Again, hopefully not silly and not nagging: is the bulb carrier a "fork" ? from the bottom photo it appears that the machine screw passes through a slot and not a hole. Perhaps the carrier could slide downwards ? or disassembled, inverted by 180 then reassembled ?

Hobbyst46 wrote: ↑

Wed Apr 15, 2020 12:52 pm

Michael,
Again, hopefully not silly and not nagging: is the bulb carrier a "fork" ? from the bottom photo it appears that the machine screw passes through a slot and not a hole. Perhaps the carrier could slide downwards ? or disassembled, inverted by 180 then reassembled ?

Feel free to nag ... it’s an interesting puzzle

But NO : The carrier cannot slide downwards far enough to be effective ... and even if it could, the contraption would then most probably not fit through the bayonet hole in the cover
[it’s already a wriggle, as is]
. .
Just to be clear about the problem :
1. The filament needs to be aligned with the centre of rotation of the bayonet, and I don’t think that is at all practical with this bulb
2. The mask has obviously been made to align with the filament of this bulb.

I’m happy to take more photos if you need to see a particular detail.

MichaelG.

I wonder if this might be an instance of someone copying a design without fully understanding it.

Just saw this one on ebay:
https://www.ebay.co.uk/i/402038019250

... but there is no bulb, or mask shown; so cannot do a useful comparison with mine.

MichaelG.

MichaelG. wrote: ↑

Thu Apr 16, 2020 8:33 am

Just saw this one on ebay:
https://www.ebay.co.uk/i/402038019250

... but there is no bulb, or mask shown; so cannot do a useful comparison with mine.

MichaelG.

(1) But, the short section (red frame) of the metal carrier of the bulb, I mean the section onto which the bulb seats, in the eBay item, is different from the one in your illuminator. It appears to be slightly shorter, relative to the opposite long section, than on your illuminator.
Maybe, just filing or sawing that carrier will lower the bulb ?

(2) Is the mask (yellow frame) really necessary ?

Thanks for the further suggestion ... But, I think perhaps it is time to say [hopefully not too bluntly] that I already have at least three options, any of which, I am sure, will fix the problem.

The only reason I shared this [under its rather flippant title] was to make others aware of a design/manufacturing error that I had never seen mentioned elsewhere.

Please don’t think me unappreciative !!

MichaelG.

The only reason I shared this [under its rather flippant title] was to make others aware of a design/manufacturing error that I had never seen mentioned elsewhere.

So that would make them rhetorical images ;)